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Abstract:

There is provided a light-emitting element which includes a first
semiconductor layer, a second semiconductor layer having an electrical
conductivity that is different from that of the first semiconductor layer
and an active layer disposed between the first and second layers, and a
first and second electrodes respectively disposed on surfaces of the
first and second semiconductor layers. The first electrode comprises a
plurality of electrode pieces separated from each other; and each of the
electrode pieces comprises a power feed pad, and an extended portion
connected to the pad and that extends in a direction away from the pad,
and a terminal end portion of the extended portion of an electrode piece
is opposed to a terminal end portion of the extended portion of the other
electrode piece across a gap.

Claims:

1. A semiconductor light-emitting element comprising a first
semiconductor layer having a first electrical conductivity, a second
semiconductor layer having a second electrical conductivity that is
different from said first electrical conductivity, an active layer
disposed between said first semiconductor layer and said second
semiconductor layer, and a first electrode and a second electrode
respectively disposed on surfaces of the first and second semiconductor
layers, wherein said first electrode comprises a plurality of electrode
pieces separated at a distance from each other; and each of said
plurality of electrode pieces comprises a power feed pad, and an extended
portion that is connected to said power feed pad and that extends in a
direction away from said power feed pad, and a terminal end portion of
said extended portion of an electrode piece is opposed to a terminal end
portion of said extended portion of the other electrode piece across a
gap.

2. The semiconductor light-emitting element according to claim 1, wherein
said plurality of electrode pieces forms a point symmetric pattern on a
surface of the first semiconductor layer.

3. The semiconductor light-emitting element according to claim 1, wherein
each of said power feed pads is arranged in a peripheral portion of said
first semiconductor layer; and each of said extension portions extends
from the peripheral portion toward the center portion of said first
semiconductor layer.

4. The semiconductor light-emitting element according to claim 1, wherein
said extension portions form a comb pattern.

5. The semiconductor light-emitting element according to claim 1, wherein
said first electrode includes an auxiliary electrode piece that extends
within said gap.

6. A flash light device provided with the semiconductor light-emitting
element according to claim 1, the flash light device comprising a
controller for feeding drive current to said semiconductor light-emitting
element via each of said plurality of electrode pieces.

7. The flash light device according to claim 6, wherein said controller
switches between a flash light-emitting mode for feeding drive current to
each of said plurality of electrode pieces so that said semiconductor
light-emitting element emits a photoflash, and a continuous
light-emitting mode for feeding drive current that is less than the drive
current in said flash light-emitting mode to some of said plurality of
electrode pieces so that said semiconductor light-emitting element emits
continuous light.

8. The flash light device according to claim 6, wherein said controller
carries out a first step for feeding drive current to any of said
plurality of electrode pieces so that said semiconductor light-emitting
element emits a photoflash, and thereafter carries out a second step for
feeding drive current to electrode pieces that are different from the
electrode pieces to which drive current was fed in said first step so
that said semiconductor light-emitting element emits a photoflash.

9. The flash light device according to claim 8, further comprising a lens
for projecting the photoflash emitted in said first step and the
photoflash emitted in said second step mutually in the same lighting
range.

10. The flash light device according to claim 6, further comprising a
lens having a single focus for said plurality of electrode pieces, above
said semiconductor light-emitting element.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field The present invention relates to a semiconductor
light-emitting element and a flash light device having the semiconductor
light-emitting element. 2. Description of the Related Art

[0002] There is known an image pickup device provided with a strobe or
flash light device that uses a light-emitting diode (LED) as a light
source. Also known is an image pickup device having a variable
light-distribution mechanism for suitably directing illumination light on
an object in an image pickup area (or angle of view) in a flash light
device.

[0003] For example, Japanese Laid-open Patent Publication No. 2005-338280
(hereinafter referred to as Patent Document 1) describes constituting a
light source using a plurality of light-emitting diodes, and varying the
number of light-emitting diodes that are lit or illuminate in accordance
with focal distance information of an image pickup lens to thereby obtain
a required lighting angle of illumination light.

[0004] Also, Japanese Laid-open Patent Publication No. 2008-102199
(hereinafter referred to as Patent Document 2) describes an illumination
or lighting device in which a light-emitting region of a single
light-emitting element is divided by dividing a cathode electrode, and
any of the light-emitting regions is caused to emit light in accordance
with the angle of view of the image pickup device.

[0005] Also, Japanese Domestic Republication No. 2008-529095 (hereinafter
referred to as Patent Document 3) describes an illumination device used
together with a camera, wherein the light-emitting element includes two
or more light-emitting zones, and the light-emitting zones are
individually and selectively controlled and emit intensity-controlled
light.

[0006] Also, Japanese Laid-open Patent Publication No. 2008-28269
(hereinafter referred to as Patent Document 4) describes an illumination
device configured by forming a plurality of dispersed electrodes on the
surface of a light-emitting element, and connecting a drive circuit to
each of the dispersed electrodes.

SUMMARY OF THE INVENTION

[0007] When the light source is composed of a plurality of light-emitting
elements in the same manner as the illumination device described in
Patent Document 1, light distribution control is facilitated because the
light emission points are completely separated from each other. However,
there are cases in which position offsets are readily generated in the
mounting positions of the light-emitting elements and the formation of
light distribution is compromised. Also, there is a problem in that it is
difficult to reduce the size of the device and the number of components
is increased because the surface area of the mounting substrate on which
the light-emitting elements are arranged is increased. In terms of
solving the problems described above, it is effective to use a
configuration so that the light-emitting region of the light-emitting
elements is divided and so that the light-emitting regions can be
individually controlled, as described in Patent Documents 2 to 4.

[0008] The ability to form a desired light emission intensity distribution
in an image pickup area (or angle of view) is important in terms of
realizing variable light-distribution in a flash light device. For
example, when an object is positioned leftward from the center in the
image pickup area, it is necessary to form light distribution so that the
left side in the image pickup area becomes brighter. It is not easy to
form such a light distribution by merely individually controlling the
light-emitting region divided in terms of the light-emitting elements. It
is preferred that a plurality of light-emitting regions be configured so
as to be regarded as a plurality of light sources in order to carry out
such light distribution control. In other words, it is preferred that the
light-emitting elements be configured so that the light radiated
simultaneously from a plurality of light-emitting regions is perceived to
be a plurality of light emission points.

[0009] The present invention was contrived in view of the foregoing
matters, it being an object thereof to provide a flash light device
capable of forming a desired light distribution in an image pickup area,
and a semiconductor light-emitting element used in the flash light
device.

[0010] According to the present invention, there is provided a
semiconductor light-emitting element comprising a first semiconductor
layer having a first electrical conductivity, a second semiconductor
layer having a second electrical conductivity that is different from the
first electrical conductivity, an active layer disposed between the first
semiconductor layer and the second semiconductor layer, and a first
electrode and a second electrode respectively disposed on surfaces of the
first and second semiconductor layers, wherein

[0011] the first electrode comprises a plurality of electrode pieces
separated at a distance from each other; and

[0012] each of the plurality of electrode pieces comprises a power feed
pad, and an extended portion that is connected to the power feed pad and
that extends in a direction away from the power feed pad, and a terminal
end portion of the extended portion of an electrode piece is opposed to a
terminal end portion of the extended portion of the other electrode piece
across a gap.

[0013] The flash light device according to the present invention is a
flash light device having the semiconductor light-emitting element
described above, the flash light device comprising a controller for
feeding a drive current to the semiconductor light-emitting element via
each of the plurality of electrode pieces.

[0014] In accordance with the semiconductor light-emitting element and the
flash light device having the semiconductor light-emitting element
according to the present invention, the extension portions constituting
the first and second electrode pieces extend in a direction away from the
power feed pads, which are points for applying electric current, and have
a resistance component that increases along the extension direction of
the extension portions. Consequently, the electric current density in the
terminal end portions of the extension portions is relatively low. Since
the terminal end portions of the extension portions face (i.e., are
opposed to) each other across a gap, a portion having a relatively low
electric current density, i.e., a portion having relatively low light
emission intensity is formed in the gap portion in the semiconductor
film. A plurality of light-emitting portions formed on the semiconductor
light-emitting element is arranged so that the portion in which the light
emission intensity is relatively lower is disposed between the
light-emitting portions. The light radiated simultaneously from the
plurality of light-emitting portions can thereby be perceived as a
plurality of light emission points. In other words, the plurality of
light-emitting portions are regarded to be a plurality of independent
light sources, and it is therefore possible to readily form a desired
light-distribution.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a functional block view showing the configuration of the
flash light device 1 according to a first embodiment of the invention;

[0016]FIG. 2A is a plan view showing a detailed configuration of the
light source portion according to the first embodiment of the invention,
FIG. 2B is a cross-sectional view along the line 2b-2b in FIG. 2A, and
FIG. 2C is a cross-sectional view showing the state of drive current that
flows inside the LED chip according to the embodiment of the invention;

[0017]FIG. 3A is a chart showing modes of drive current control for the
light-emitting portions that correspond to each light-distribution
pattern, and FIGS. 3B to 3D are graphs showing light emission intensity
distributions on an LED chip that correspond to each light-distribution
pattern;

[0018] FIGS. 4A to 4C are diagrams showing the lighting ranges of the
illumination light that correspond to each light-distribution pattern;

[0019]FIG. 5 is a plan view showing the configuration of the light source
portion according to a second embodiment of the invention;

[0020]FIG. 6A is a chart showing modes of drive current control for the
light-emitting portions that correspond to each light-distribution
pattern, and FIGS. 6B to 6E are graphs showing light emission intensity
distributions on an LED chip that correspond to each light-distribution
pattern;

[0021]FIG. 7 is a diagram showing the lighting range of the illumination
light that corresponds to the light-distribution pattern;

[0022] FIG. 8 is a plan view showing the configuration of the light source
portion according to a third embodiment of the invention;

[0023]FIG. 9A is a chart showing modes of electric current control for
each light-emitting portion in accordance with the range of the image
pickup area, and FIGS. 9B and 9C are diagrams showing lighting range of
the illumination light that corresponds to the electric current control
shown in FIG. 9A;

[0024] FIG. 10 is a chart showing modes of electric current control for
each light-emitting portion in the flash light-emitting mode and the
continuous light-emitting mode;

[0025]FIG. 11A is a plan view showing the configuration of the light
source portion 2 according to the fourth embodiment of the invention, and
FIG. 11B is a cross-sectional view along the line 11a-11b in FIG. 11A;
and

[0026]FIG. 12A is a chart showing modes of electric current control for
each light-emitting portion in the preliminary light-emitting mode and
the flash light-emitting mode, and FIGS. 12B and 12C are diagrams showing
the lighting range of the illumination light during preliminary light
emission and flash light emission, respectively.

DETAILED DESCRIPTION OF THE INVENTION

[0027] The flash light device according to embodiments of the present
invention is described below with reference to the attached drawings. In
the drawings, the same reference numerals are used for the same or
essentially the same or equivalent constituent elements and portions.

First Embodiment

[0028]FIG. 1 is a functional block view showing the configuration of the
flash light device 1 according to a first embodiment of the invention.
The flash light device 1 is provided as an accessory to, e.g., a digital
camera or other image pickup device, and is a device for directing
illumination light toward an image pickup area during photography or at
other times.

[0029] A power source 10 is a DC power source for generating illumination
light in a light source portion 20. The power source 10 may double as a
power source of the image pickup device to which the flash light device 1
is accessory. A booster circuit 11 boosts the DC voltage generated by the
power source 10 to a voltage required for generating illumination light
in the light source portion 20. In other words, the booster circuit 11
generates voltage that is greater than a forward voltage VF of
light-emitting diodes constituting the light source portion 20. The
booster circuit 11 is composed of, e.g., a charge pump-type or
chopper-type DC-DC converter. The DC voltage boosted by the booster
circuit 11 is fed to an anode electrode of a light-emitting diode (LED)
chip 220 constituting the light source portion 20.

[0030] The light source portion 20 generates illumination light using the
electric power fed from the power source 10 as drive power, and directs
the illumination light toward the image pickup area. The light source
portion 20 includes a single LED chip 220. The LED chip 220 has a
plurality of light-emitting portions that can be mutually isolated and
independently controlled. In the present embodiment, the case in which
the LED chip 220 has two light-emitting portions is used as an example.
Each of the mutually isolated light-emitting portions is connected to a
drive circuit 30. The configuration of the light source portion 20 is
later described in greater detail.

[0031] The drive circuit 30 independently controls the drive current of
the plurality of light-emitting portions formed in the LED chip 220, on
the basis of control signals from the controller 40. The drive circuit 30
has, e.g., a variable current circuit connected to each of the cathode
electrodes of the LED chip 220. Each of the plurality of light-emitting
portions emits light at a light emission intensity that corresponds to
the magnitude of the independently controlled drive current. In other
words, the plurality of light-emitting portions can emit light at light
emission intensities different from each other.

[0032] A controller 40 controls the light emission of the LED chip 220 on
the basis of, e.g., control signals from a host device that controls the
operation of the image pickup device overall, or on the basis of
operational input from a user. In other words, the controller 40 turns
light-emitting portions of the LED chip 220 on and off, sets the
light-emission intensity or the like, and feeds control signals to the
booster circuit 11 and the drive circuit 30, on the basis of commands
from the exterior. The booster circuit 11 boosts the voltage in
accordance with the control signal fed from the controller 40, and stops
boosting voltage at a set voltage value. The drive circuit 30 controls
the amount of electric current applied to the light-emitting portions of
the LED chip 220 on the basis of a control signal (e.g., electric current
command value) fed from the controller 40.

[0033] A protection circuit 50 is provided with the aim of protecting the
LED chip 220, and may include, e.g., a Zener diode, a varistor, a
capacitor or other element for absorbing a surge voltage applied to the
LED chip 220, a thermal conduction chip (e.g., Japanese Laid-open Patent
Application No. 2010-267834) or other element for radiating heat from the
LED chip 220, and a thermistor or other heat detection element for
detecting the junction temperature of the LED chip 220.

[0034] A capacitor 60 constitutes charge-accumulating means provided as
required in the case that a flash of light (i.e., photoflash) is
generated in the light source portion 20. The flash of light requires a
greater drive current, and accordingly there are cases in which the
operation of other devices (e.g., the image pickup device) that share the
power source 10 will become unstable when the drive current directly
feeds from the power source 10. In view of this situation, a charge is
temporarily accumulated in the capacitor 60 when a flash of light is to
be generated, and a drive current is fed from the capacitor 60 to the
light-emitting portions inside the LED chip. A switch 70 switches the
connection destination of the capacitor 60 to the booster circuit 11 or
any of the anode lines in accordance with a control signal from the
controller 40 to thereby charge and discharge the capacitor 60. The
voltage stop function of the booster circuit may be included in the drive
circuit, and the switch 70 is not required in this case.

[0035]FIG. 2A is a plan view showing the configuration of the light
source portion 20 in greater detail. FIG. 2B is a cross-sectional view
along the line 2b-2b in FIG. 2A, and FIG. 2C is a cross-sectional view
showing the state of drive current that flows inside the LED chip 220.

[0036] A substrate 210 is constructed from a board material composed of,
e.g., ceramic, glass epoxy resin, or another insulator. The substrate 210
has a die pad 211 composed of an electroconductor on the chip mounting
surface on which the LED chip 220 is mounted, and two bonding pads 212
that correspond to a first light-emitting portion 301 and a second
light-emitting portion 302 formed on the LED chip 220. The die pad 211 is
connected to the booster circuit 11, and the bonding pads 212 are
connected to the drive circuit 30. A single LED chip 220 is mounted on
the die pad 211. An anode electrode 222 disposed on the mounting surface
side of the LED chip 220 is joined to the die pad 211 via an
electroconductive die attachment material (not shown). The cathode
electrode 223 disposed on the light extraction plane side of the LED chip
220 is connected to the bonding pads 212 via bonding wires 230. A solder
connection using reflow or another suitable method may be used in place
of the connection via the bonding wires 230 as long as the electrical
connection relationship is the same.

[0037] The LED chip 220 has: a semiconductor film 221 formed by layering
an n-type semiconductor layer, an active layer, and a p-type
semiconductor layer composed of, e.g., GaN-based semiconductors; an anode
electrode (p-electrode) 222 provided so as to cover substantially the
entire surface of the p-type semiconductor layer disposed on the mounting
surface side of the semiconductor film 221; and a cathode electrode
(i.e., n-electrode) 223 provided to the surface of the n-type
semiconductor layer arranged on the light extraction plane side of the
semiconductor film 221. The anode electrode and the cathode electrode are
in, e.g., a "vertical" configuration arranged on the obverse and reverse
surfaces, respectively, of the semiconductor film, but the anode
electrode and the cathode electrode may also be in a "lateral"
configuration arranged on the same surface of the semiconductor film.

[0038] The cathode electrode 223 is composed of a first electrode piece
223a and a second electrode piece 223b that are set at a distance from
each other on the surface of the n-type semiconductor layer. In this
manner, the first light-emitting portion 301 and the second
light-emitting portion 302 separated at a distance from each other can be
formed inside the LED chip 220. The first and second electrode pieces
223a, 223b include pad portions 224a, 224b, respectively, and extension
portions 225a, 225b, respectively.

[0039] Each of the pad portions 224a, 224b is disposed in the peripheral
portion of the LED chip 220. The pad portions 224a, 224b are connected to
the bonding pads 212, respectively, on the substrate 210 via the bonding
wires 230. The extension portions 225a, 225b are connected to the pad
portions 224a, 224b, respectively, and extend from the peripheral portion
of the LED chip 220 toward the center portion (i.e., away from the pad
portions 224a, 224b). The extension portions 225a, 225b may have a
pectinate or comb pattern as shown in FIG. 2A. The extension portions
225a, 225b terminate just short of the center line of the chip surface
and do not mutually intersect or couple together. In other words, the
terminal end portion of the extension portion 225a of the first electrode
piece and the terminal end portion of the extension portion 225b of the
second electrode piece face (i.e., are opposed to) each other across a
gap in the center portion of the chip. The extension portions 225a, 225b
are preferably set at a sufficient distance from each other so that
electric currents spreading from the terminal end portions thereof do not
merge together. The first and second electrode pieces 223a, 223b are
arranged side by side along the extended direction of the extension
portions 225a, 225b. The cathode electrode 223 composed of the first and
second electrode pieces 223a, 223b is formed in a point-symmetric pattern
about the center point of the light extraction plane (i.e., the obverse
surface of the n-type semiconductor layer) of the LED chip 220.

[0040] The first and second electrode pieces 223a, 223b are connected to
the drive circuit 30 via the bonding wires 230, which are connected to
the pad portions 224a, 224b, respectively, and independently controlled
drive current is fed to the first and second light-emitting portions 301,
302.

[0041] When drive current is applied to each of the light-emitting
portions, the electric current density directly below the pad portions
224a, 224b, which are electric current application points, is increased
in a relative manner, as shown in FIG. 2C. The extension portions 225a,
225b have a resistance component that increases along the direction of
extension, and the electric current density directly below the terminal
end of the extension portions 225a, 225b is therefore reduced in a
relative manner. The terminal end portions of the extension portions
225a, 225b are concentrated in the center portion of the chip surface and
a region of low electric current density is therefore formed in the
center portion of the chip. In other words, the light emission intensity
in the light extraction plane of the LED chip become relatively high at
the peripheral portions or end portions of the chip in which the pad
portions 224a, 224b are disposed, and gradually decreases in progression
to the center portion of the chip (see FIG. 3B). In this manner, in
accordance with the configuration of the cathode electrode 223 according
to the present embodiment, the light simultaneously radiated from two
light-emitting portions can be perceived as two light emission points
because a portion having relatively low light emission intensity is
formed between the first light-emitting portion 301 and the second
light-emitting portion 302. The extension portions 225a, 225b have a
pectinate or comb pattern, whereby the electric current density
distribution in the direction orthogonal to the direction of extension of
the extension portions 225a, 225b (i.e., the direction in which the lines
are arrayed) becomes uniform and the light emission intensity
distribution in the stated direction becomes uniform.

[0042] A fluorescent-substance containing resin 240 is disposed on the
substrate 210 so as to embed the LED chip 220. The fluorescent-substance
containing resin 240 is composed of a resin material in which a YAG:Ce
fluorescent substance is dispersed in silicone resin or another
light-transmissive resin. The YAG:Ce fluorescent substance absorbs blue
light having peak wavelength of, e.g., 460 nm that is radiated from the
LED chip 220, and converts the absorbed blue light into yellow light
having a light emission peak at a wavelength of, e.g., about 560 nm.
White light is obtained from the light source portion 20 by a mixture of
the yellow light having a wavelength converted by the fluorescent
substance and the blue light transmitted through the
fluorescent-substance containing resin 240 without undergoing wavelength
conversion. When white light is desired, apart from using a YAG:Ce
fluorescent substance, it is also possible to use a fluorescent substance
that absorbs blue light emitted from the LED chip 220 to emit a yellow
fluorescent light, or to use a known mixture in a suitable ratio of
fluorescent substances that emit red color and/or green color. In the
case that a light of a color other than white is desired, it is possible
to include in the resin for embedding the LED chip 220 a fluorescent
substance that emits a fluorescent light which does not have a
complementary relationship with the light emitted from the LED chip 220,
to use a transparent resin that does not contain a fluorescent substance,
or to eschew the use of a resin itself.

[0043] When the fluorescent substance-containing resin 240 is used, the
thickness is more preferably low so that the formation of light
distribution is not compromised in the later-described image pickup area.
The thickness is preferably 300 μm or less.

[0044] A lens 250 is disposed above (i.e., forward in the light projection
direction) the fluorescent-substance-containing resin 240. The lens 250
is composed of acrylic, carbonate, silicone, epoxy, urethane, liquid
crystal polymer, or another light-transmissive resin having a higher
refractive index than air. The lens 250 projects light from the LED chip
220 onto a lighting surface so that the lighting range of the
illumination light covers the entire image pickup area. The lens 250 has
a single focal point or focus for the plurality of light-emitting
portions formed in the LED chip 220, and the light emission intensity
distribution that appears on the light extraction plane of the LED chip
220 is reproduced on the light radiation surface. The lens surface for
controlling light-distribution may be disposed on the LED chip side or
the light radiation surface side.

[0045] The operation of the flash light device 1 having the
above-described configuration is described below. According to the flash
light device 1 of the embodiment of the invention, three typical
light-distribution patterns can be achieved as shown in the example
described below. FIG. 3A is a chart showing the modes of drive current
control for each light-emitting portion that corresponds to each of the
above-noted three light-distribution patterns, and shows the relative
relationship of the amount of electric current applied to first and
second light-emitting portions 301, 302. In FIG. 3A, the circle indicates
that the applied electric current amount is comparatively high, and the
triangle indicates that the applied electric current amount is relatively
low. FIGS. 3B to 3D are graphs schematically showing light emission
intensity distributions on the light extraction plane of the LED chip 220
that correspond to each of three light-distribution patterns,
respectively, and show the light emission intensity distribution on a
line that connects the pad portion 224a and the pad portion 224b. FIGS.
4A to 4C are diagrams schematically showing the lighting ranges of the
illumination light that correspond to each of the three
light-distribution patterns.

[0046] The first light-distribution pattern (or light-distribution
pattern-1) is used for forming a light-distribution that does not have
bias in the left and right brightness inside the image pickup area (or
angle of view). The controller 40 receives a control signal indicating
that an object O is positioned in the center of an image pickup area X,
as shown in FIG. 4A, from a CPU (not shown) or the like for operating and
controlling the entire image pickup device, and thereupon generates and
feeds an electric current command value, which sets the first and second
light-emitting portions 301, 302 to the same light emission intensity as
each other, to the drive circuit 30. The drive circuit 30 controls the
drive current so that the electric current amounts applied to the first
and second light-emitting portions 301, 302 are equal to each other on
the basis of the electric current command value. In accordance therewith,
the first and second light-emitting portions 301, 302 on the LED chip 220
emit light with the same light emission intensity as each other. As a
result, a light emission intensity distribution in which a peak appears
at the two end portions is formed in the light extraction plane of the
LED chip 220, as shown in FIG. 3B. The light emitted from the LED chip
220 is directed via the lens 250 onto the object O so as to cover the
entire image pickup area X, as shown in FIG. 4A. The illumination light
is directed onto the object O positioned in the center of the image
pickup area X with an unbiased light-distribution in the image pickup
area X.

[0047] The second light-distribution pattern (or light-distribution
pattern-2) forms a light distribution in which the left side in the image
pickup area is brighter. The controller 40 receives a control signal
indicating that an object O is positioned at the left end of the image
pickup area X, as shown in FIG. 4B, and thereupon generates and feeds to
the drive circuit 30 an electric current command value for setting the
light emission intensity in the first light-emitting portion 301 to be
relatively greater. The drive circuit 30 controls the drive current so
that the electric current amount applied to the first light-emitting
portion 301 is greater than the electric current amount applied to the
second light-emitting portion 302 on the basis of the electric current
command value. In accordance therewith, the first light-emitting portion
301 on the LED chip 220 emits light having a greater light emission
intensity than that of the second light-emitting portion 302. As a
result, a light emission intensity distribution in which a peak appears
on the left side is formed in the light extraction plane of the LED chip
220, as shown in FIG. 3C. The light emitted from the LED chip 220 is
directed via the lens 250 onto the object O so as to cover the entire
image pickup area X, as shown in FIG. 4B. The illumination light is
directed onto the object O positioned at the left end of the image pickup
area X with a light distribution in which the left side is brighter in
the image pickup area X.

[0048] The third light-distribution pattern (or light-distribution
pattern-3) forms a light distribution in which the right side of the
image pickup area is brighter. The controller 40 receives a control
signal indicating that an object O is positioned at the right end of the
image pickup area X, as shown in FIG. 4C, and thereupon generates and
feeds to the drive circuit 30 an electric current command value for
setting the light emission intensity in the second light-emitting portion
302 to be relatively greater. The drive circuit 30 controls the drive
current so that the electric current amount applied to the second
light-emitting portion 302 is greater than the electric current amount
applied to the first light-emitting portion 301 on the basis of the
electric current command value. In accordance therewith, the second
light-emitting portion 302 on the LED chip 220 emits light with a light
emission intensity that is greater than that of the first light-emitting
portion 301. As a result, a light emission intensity distribution in
which a peak appears on the right side is formed in the light extraction
plane of the LED chip 220, as shown in FIG. 3D. The light emitted from
the LED chip 220 is directed via the lens 250 onto the object O so as to
cover the entire image pickup area X, as shown in FIG. 4C. The
illumination light is directed onto the object O positioned at the right
end of the image pickup area X with a light distribution in which the
right side is brighter in the image pickup area X.

[0049] In this manner, the LED chip 220 according to the first embodiment
of the invention has first and second electrode pieces 223a, 223b
separated at a distance from each other on the chip surface, and has, as
a result, two first and second light-emitting portions 301, 302 divided
at a distance from each other. The first and second electrode pieces
223a, 223b have pad portions 224a, 224b, respectively, disposed at the
peripheral portion of the LED chip, and extension portions 225a, 225b,
respectively, that are connected to the pad portions 224a, 224b and that
extend in a direction away from the pad portions 224a, 224b (i.e., toward
the center portion of the chip). The terminal end portions of the
extension portions 225a, 225b face each other across a gap in the center
portion of the LED chip. The extension portions 225a, 225b have a
resistance component that increases along the extension direction
thereof, and therefore have an electric current density at the terminal
end portions that decreases in a relative manner. Therefore, a portion in
which the electric current density is relatively lower, i.e., a portion
in which the light emission intensity is relatively lower, is formed in
the center portion of the LED chip. The two first and second
light-emitting portions 301, 302 formed on the LED chip are arranged so
that the portion in which the light emission intensity is relatively
lower is disposed therebetween. In this manner, the light emitted
simultaneously from the two first and second light-emitting portions 301,
302 can be perceived as two light emission points. In other words, the
two light-emitting portions are regarded as two independent light
sources, and it is therefore possible to readily form a desired light
distribution, as shown in FIGS. 4A to 4C.

Second Embodiment

[0050]FIG. 5 is a plan view showing the configuration of a light source
portion 20A provided to the flash light device according to a second
embodiment of the invention. The configuration of the cathode electrode
of the LED chip 220A constituting the light source portion 20A is
modified in comparison with the LED chip 220 according to the first
embodiment described above. A cathode electrode 223A of the LED chip 220A
has a first electrode piece 223a, a second electrode piece 223b, and an
auxiliary electrode piece 223z. The configuration of the first and second
electrode pieces 223a, 223b is the same as those of the LED chip 220
according to the first embodiment described above. The auxiliary
electrode piece 223z is composed of: an extension portion 225z that
extends inside a gap formed between terminal end portions of an extension
portion 225a of the first electrode piece and an extension portion 225b
of the second electrode piece; and a pad portion 224z connected to the
extension portion 225z and arranged on the peripheral portion of the
chip. The pad portion 224z is connected to bonding pads 212 on a
substrate 210 via bonding wires 230 and is connected to the drive circuit
30. Thus, the auxiliary electrode piece 223z set at a distance from the
first and second electrode pieces 223a, 223b is disposed on the LED chip,
whereby an auxiliary light-emitting portion 310 that can be independently
controlled between a first light-emitting portion 301 and a second
light-emitting portion 302 is formed on the LED chip. The other
constituent portions other than the light source portion 20A are the same
as those of the flash light device of the first embodiment described
above.

[0051] In accordance with the flash light device provided with the LED
chip 220A according to the second embodiment, four typical
light-distribution patterns as described below can be achieved. FIG. 6A
is a chart showing modes of drive current control for each of the
light-emitting portions that corresponds to each of the four
light-distribution patterns mentioned above, and shows the relative
relationship between the electric current amounts applied to the first
and second light-emitting portions 301, 302 and the auxiliary
light-emitting portion 310. In FIG. 6A, the circle indicates that the
applied electric current amount is comparatively high, and the triangle
indicates that the applied electric current amount is comparatively low.
FIGS. 6B to 6E are graphs showing light emission intensity distributions
on the light extraction plane of the LED chip 220A that correspond to
each of the four light-distribution patterns. FIG. 7 is a diagram showing
the lighting ranges of the illumination light that corresponds to the
four later-described light-distribution patterns.

[0052] The first to third light-distribution patterns are the same as
those of the flash light device according to the first embodiment
described above. In other words, the first light-distribution pattern
forms a light distribution unbiased in left and right brightness in the
image pickup area (see FIG. 6B). In the case that such a light
distribution is formed, the amount of electric current applied to the
first light-emitting portion 301 and the second light-emitting portion
302 is the same, and the amount of electric current applied to the
auxiliary light-emitting portion 310 is relatively low. The second
light-distribution pattern forms a light distribution in which the left
side in the image pickup area becomes brighter (see FIG. 6C). In the case
that such a light distribution is formed, the amount of electric current
applied to the first light-emitting portion 301 is relatively increased
and the amount of electric current applied to the second light-emitting
portion 302 and the auxiliary light-emitting portion 310 is relatively
reduced. The third light-distribution pattern forms a light distribution
in which the right side in the image pickup area becomes brighter (see
FIG. 6D). In the case that such a light distribution is formed, the
amount of electric current applied to the second light-emitting portion
302 is relatively increased and the amount of electric current applied to
the first light-emitting portion 301 and the auxiliary light-emitting
portion 310 is relatively reduced.

[0053] The fourth light-distribution pattern (or light-distribution
pattern-4) forms a light distribution having a light emission intensity
peak in the center and in the left and right sides in the image pickup
area (see FIG. 6E). In the case that such a light distribution is formed,
the amounts of electric current applied to the first light-emitting
portion 301, the second light-emitting portion 302, and the auxiliary
light-emitting portion 310 are the same. In accordance with the fourth
light-distribution pattern, it is possible to illuminate an object O
positioned in the center of the image pickup area, as shown in, e.g.,
FIG. 7, using illumination light having higher light emission intensity.

[0054] In accordance with the configuration of the cathode electrode of
the LED chip 220 according the first embodiment described above, a low
electric current density region is formed in the center portion of the
chip, and therefore a portion in which the light emission intensity is
relatively low is formed in the center portion of the chip in the case
that the first and second light-emitting portions 301, 302 are made to
emit light simultaneously. Accordingly, it is difficult to form a light
distribution in which the center portion of the image pickup area is made
relatively brighter. On the other hand, the cathode electrode of the LED
chip 220A according to the second embodiment furthermore has an auxiliary
electrode piece 223c having the extension portion 225z that extends into
the low electric current density region in the first embodiment (i.e.,
the gap between the first electrode piece 223a and the second electrode
piece 223b). In accordance with this electrode configuration, it is
possible to also apply a drive current to the center portion of the LED
chip, and to form a light distribution in which the center portion of the
image pickup area becomes relatively brighter.

Third Embodiment

[0055] FIG. 8 is a plan view showing the configuration of the light source
portion 20B provided to the flash light device according to a third
embodiment of the invention. An LED chip 220B constituting a light source
portion 20B has a cathode electrode composed of first to sixth electrode
pieces 223a to 223f that are set at a distance from each other. The six
electrode pieces 223a to 223f are composed of extension portions 225a to
225f having a comb pattern or shape, and pad portions 224a to 224f,
respectively, in similar fashion to the first electrode piece 223a and
the second electrode piece 223b according to the first embodiment
described above. The six electrode pieces 223a to 223f are disposed in an
array so that a pair composed of the first electrode piece 223a and the
second electrode piece 223b in the first embodiment line up in the
vertical direction in the drawing. The cathode electrode composed of the
first to sixth electrode pieces 223a to 223f forms a point symmetric
pattern about the center point of the light extraction plane of the LED
chip.

[0056] The mutually adjacent electrode pieces 223a to 223b, 223c to 223d,
223e to 223f are arranged so that the terminal end portions of the
extension portions are opposed to each other across a gap in the center
portion of the chip. The terminal end portions of the extension portions
225a to 225f are concentrated in the center portion of the chip surface,
and a low electric current density region is therefore formed in the
center portion of the LED chip.

[0057] The pad portions 224a to 224f are connected to the drive circuit 30
via bonding wires 230. Thus, the six electrode pieces 223a to 223f are
set at a distance from each other on the LED chip 220B, whereby first to
sixth light-emitting portions 301 to 306 capable of being independently
controlled are formed on the LED chip 220B. When drive current is applied
to the light-emitting portions, the light emission intensity in the
peripheral portion of the chip where the pad portions 224a to 224f are
disposed increases in a relative manner, and a light emission intensity
distribution is formed in which the light emission intensity gradually
decreases in progression toward the center portion of the chip. The other
constituent portions other than the light source portion 20B are the same
as those of the flash light device of the first embodiment described
above.

[0058] When the focal distance of the lens system in the image pickup
device is varied, the range (or size) of the image pickup area (or angle
of view) is also varied. In accordance with the flash light device
provided with the LED chip 220B according to the present embodiment, it
is possible to advantageously control light distribution such as varying
the lighting range of the illumination light in accordance with the
variation of the range (size) of the image pickup area.

[0059]FIG. 9A is an example of modes of electric current control for each
light-emitting portion in accordance with the range (size) of the image
pickup area, and FIGS. 9B and 9C are diagrams showing lighting range of
the illumination light that corresponds to the electric current control
shown in FIG. 9A.

[0060] When the controller 40 receives information related to the range of
the image pickup area from the CPU or the like for controlling the
operation of the image pickup device overall, the controller generates
and feeds to the drive circuit 30 an electric current command value that
corresponds to the range (size) of the image pickup area. The drive
circuit 30 controls the amount of electric current applied to the first
to sixth light-emitting portions 301 to 306 on the basis of the electric
current command value.

[0061] For example, in the case that the range of the image pickup area
(or angle of view) has become comparatively great because the lens system
of the image pickup device has moved to the wide angle side and the focal
distance has become comparatively short, the amount of electric current
applied to the first to sixth light-emitting portions 301 to 306 is
controlled so as to be comparatively high, as shown in the upper part of
FIG. 9A. The first to sixth light-emitting portions 301 to 306 emit light
having a comparatively high light emission intensity, and illumination
light is directed onto the entire image pickup area X having a
comparatively large size, as shown in FIG. 9B.

[0062] On the other hand, in the case that the range of the image pickup
area (angle of view) has become comparatively small because the lens
system of the image pickup device has moved to the telescopic side and
the focal distance has become comparatively great, the amount of electric
current applied to the first and second light-emitting portions 301, 302
and to the fifth and sixth light-emitting portions 305, 306 is controlled
to become comparatively low, and the amount of electric current applied
to the third and fourth light-emitting portions 303, 304 is controlled to
become comparatively high, as shown in the lower part of FIG. 9A.
Although the lighting range of the illumination light in the upper and
lower parts of the image pickup area X is thereby reduced in comparison
with the case of FIG. 9B, the illumination light is directed onto the
entire image pickup area X, which has been reduced in accordance with the
focal distance, as shown in FIG. 9C. Thus, in accordance with the flash
light device provided with the LED chip 220B according to the third
embodiment, it is possible to advantageously control light distribution,
such as modifying the lighting range in accordance with the range (size)
of the image pickup area (angle of view), which is modified in accordance
with the focal distance of the image pickup device.

[0063] In a mode in which the range of the image pickup area is reduced,
it is assumed that the object is positioned far away. In this case, the
light emission time in the light source portion 20B must be extended in
order to ensure luminous exposure. In the case that a flash of light is
to be generated using a capacitor, there is a problem in ensuring light
emission time because the amount of charge that can be accumulated in the
capacitor is limited. As described above, the lighting range of the
illumination light is reduced in accompaniment with the reduction in the
range of the image pickup area, whereby the light emission time in the
light source portion 20B can be extended further. Light distribution
control such as modifying the lighting range in accordance with the range
of the image pickup area can be achieved in the LED chip according to the
first and second embodiments described above.

[0064] In accordance with the flash light device provided with the LED
chip 220B according to the third embodiment, the light source portion 20B
can generate advantageous illumination light not only in the flash
light-emitting mode for emitting a photoflash (i.e., flash of light)
having a comparatively high light emission intensity, but also in the
continuous light-emitting mode for emitting continuous light having a
comparatively low light emission intensity. FIG. 10 is a chart showing
the modes of electric current control for each of the light-emitting
portions in the flash light-emitting mode and the continuous
light-emitting mode, and shows the relative relationship of the amount of
electric current applied to light-emitting portions. In FIG. 10, the
circle indicates that the applied electric current amount is
comparatively high, the triangle indicates that the applied electric
current amount is comparatively low, the X mark indicates that the
applied amount of electric current is 0 (zero).

[0065] In the case that the controller 40 receives a control signal from
the exterior indicating that the flash light-emitting mode has been
selected, the controller generates and feeds to the drive circuit 30 an
electric current command value that corresponds to the flash
light-emitting mode. The drive circuit 30 performs electric current
control so that the amount of electric current applied to the first to
sixth light-emitting portions 301 to 306 becomes comparatively greater
(e.g., about 1 A (ampere)) during a short interval of, e.g., several tens
of milliseconds, on the basis of the electric current command value. The
first to sixth light-emitting portions 301 to 306 emit a photoflash
having a comparatively high light emission intensity in the above-noted
interval.

[0066] On the other hand, in the case that the controller 40 receives a
control signal from the exterior indicating that the continuous
light-emitting mode has been selected, the controller generates and feeds
to the drive circuit 30 an electric current command value that
corresponds to the continuous light-emitting mode. The drive circuit 30
performs electric current control so that, on the basis of the electric
current command value, the amount of electric current applied to the
third and fourth light-emitting portions 303, 304 becomes comparatively
less (e.g., about 10 mA), and the amount of electric current applied to
the remainder of the light-emitting portions becomes 0. The third and
fourth light-emitting portions 303, 304 will continuously emit light at a
comparatively low light emission intensity.

[0067] In the flash light device in which the LED chip is used, operation
is required in not only the flash light-emitting mode, but also in a
continuous light-emitting mode such as a torchlight light-emitting mode
or a video light light-emitting mode. The continuous light-emitting mode
is intended for illumination light during close-up photography or the
like, and the light emission intensity must be sufficiently suppressed in
comparison with the flash light-emitting mode. A conventional LED chip
applied to a flash light device is of a high-brightness type that can be
applied to general illumination and automotive headlights, and presumes
the use of a high-electric-current drive. For this reason, it is
difficult to stably obtain light emission in which the electric current
density inside the LED chip is dramatically reduced when the amount of
applied electric current is reduced in order to sufficiently suppress
light emission intensity.

[0068] In the flash light device according to the present embodiment, only
some of the light-emitting portions in the LED chip are made to emit
light in the continuous light-emitting mode, and it is therefore possible
to prevent a dramatic reduction in the electric current density even when
the amount of applied electric current is reduced. Operational stability
in the continuous light-emitting mode can be improved thereby. Some of
the light radiated from some of the lighted light-emitting portions is
absorbed by the non-lighted light-emitting portions, or is directed away
in a direction other than the direction in which the light is directed.
Therefore, it is possible to ensure that the light emission intensity is
even further suppressed. In this manner, it is possible to obtain an
advantageous illumination light for the flash light-emitting mode as well
as the continuous light-emitting mode, in accordance with the flash light
device according to the present embodiment.

Fourth Embodiment

[0069]FIG. 11A is a plan view showing the configuration of the light
source portion 20C provided to the flash light device according to the
fourth embodiment of the invention, and FIG. 11B is a cross-sectional
view along the line 11a-11b in FIG. 11A. The LED chip 220C constituting
the light source portion 20C has a flash light-emitting portion 320 for
performing flash light emission during photography, and a preliminary
light-emitting portion 330 for preliminarily emitting light before flash
light emission. Preliminary light emission is a function for emitting
light a single time or a plurality of times prior to photography in order
to adjust exposure and the like in an image pickup device.

[0070] The flash light-emitting portion 320 has first and second electrode
pieces 223a, 223b, which have the same configuration as those of the LED
chip 220 according to the first embodiment. In other words, the flash
light-emitting portion 320 has two independently controllable
light-emitting portions, and light distributions such as those shown in
FIGS. 4A to 4C can be formed.

[0071] A preliminary light emitting portion 330 is arranged at both end
portions of the LED chip 220C so that the flash light-emitting portion
320 is disposed therebetween. The preliminary light emitting portion 330
has an electrode piece 226 composed of: a pad portion 227 disposed at the
periphery portion of the LED chip 220C; and an extension portion 228
connected to the pad portion 227 and having a comb pattern extending into
the preliminary light emitting portion 330. The pad portion 227 is
connected to the bonding pads 212 on the substrate 210 via the bonding
wires 230, and is connected to the drive circuit 30. The preliminary
light emitting portion 330 can be controlled independent from the flash
light-emitting portion 320. The electrode piece 226 may be configured so
that the light emission intensity in the preliminary light emitting
portion 330 is substantially uniform.

[0072] The LED chip 220C is bonded onto the die pad 211 on the substrate
210 via an electroconductive die attachment material (not shown). The pad
portions 224a, 224b, 227 disposed on the LED chip are connected to the
bonding pads 212 on the substrate 210 via the bonding wires 230, and are
connected to the drive circuit 30. The fluorescent-substance containing
resin 240 is disposed on the substrate 210 so as to embed the LED chip
220C. A lens 250C is disposed above (i.e., forward in the light
projection direction) the fluorescent-substance containing resin 240.

[0073] The lens 250C has a lens surface 251 that projects light emitted
from the flash light-emitting portion 320 so as to cover the entire image
pickup area, and a lens surface 252 that projects light emitted from each
of the preliminary light emitting portions 330 so as to cover the entire
image pickup area. In other words, the lens 250C has a focal point that
corresponds to the flash light-emitting portion 320, and a focal point
that corresponds to each preliminary light emitting portion 330.

[0074]FIG. 12A is a chart showing modes of electric current control for
each light-emitting portion in the preliminary light-emitting mode and
the flash light-emitting mode. In FIG. 12A, the circle indicates that the
input of the drive current is applied to the light-emitting portion, and
an X mark indicates that the input of the drive current is not applied to
light-emitting portion.

[0075] When the controller 40 detects a shutter operation or other input
control, the controller generates and feeds to the drive circuit 30 an
electric current command value that corresponds to the preliminary
light-emitting mode. The drive circuit 30 performs electric current
control so that drive current is applied only to the preliminary light
emitting portion 330, on the basis of the electric current command value.
The preliminary light emitting portion 330 generates a single photoflash
or several photoflashes in accordance with the electric current control.
The light source portion 20C directs a photoflash having the same light
emission intensity as during the flash light-emitting mode toward the
image pickup area so as to cover the entire image pickup area. The image
pickup device adjusts the exposure and carries out other operations
during preliminary light emission.

[0076] After the preliminary light-emitting mode has ended, the controller
40 generates and feeds to the drive circuit 30 an electric current
command value that corresponds to the flash light-emitting mode. The
drive circuit 30 performs electric current control so that drive current
is applied only to the flash light-emitting portion 320, on the basis of
the electric current command value. The flash light-emitting portion 320
generates a photoflash in accordance with the electric current control.
The light source portion 20C directs a photoflash toward the image pickup
area so as to cover the entire image pickup area. The image pickup device
photographs the object while the flash light emission is being carried
out.

[0077] FIGS. 12B and 12C are diagrams showing the lighting range of the
illumination light (photoflash) directed from the light source portion
20C toward the image pickup area X during preliminary light emission and
flash light emission, respectively. The lens 250C has a focal point that
corresponds to the flash light-emitting portion 320 and each preliminary
light emitting portion 330, as described above, and performs alignment so
that the lighting range of the photoflash emitted from the flash
light-emitting portion 320 and the lighting range of the photoflash
emitted from the preliminary light emitting portion 330 match.

[0078] The interval between the end of preliminary light emission and the
start of flash light emission is generally about several tens of
milliseconds. Accordingly, in the case that the area in which preliminary
light emission is carried out and the area in which the flash light
emission is carried out in the LED chip are the same, there may be cases
in which the maximum luminous energy cannot be obtained during flash
light emission due to the effect of heat generated during preliminary
light emission. The flash light device according to the present
embodiment has the preliminary light-emitting portion and the flash
portion on a single LED chip, and only the preliminary light-emitting
portion is driven during the preliminary light-emitting mode.
Accordingly, the heat generated during preliminary light emission has
substantially no effect during flash light emission, and a flash light
emission having maximum luminous energy can be obtained.

[0079] This application is based on Japanese Patent Application No.
P2011-123270 which is hereby incorporated by reference.

Patent applications by Eiji Takashiro, Tokyo JP

Patent applications by Keima Kono, Tokyo JP

Patent applications by Tatsuma Saito, Tokyo JP

Patent applications by Tsutomu Okubo, Tokyo JP

Patent applications by Stanley Electric Co., Ltd.

Patent applications in class ELECTRIC SWITCH IN THE SUPPLY CIRCUIT

Patent applications in all subclasses ELECTRIC SWITCH IN THE SUPPLY CIRCUIT